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Journal of Materials Science & Technology 2021年第31期90卷 1-8页

作者： Huipeng Lv Chen Wu Faxiang Qin Huaxin Peng Mi Yan School of Materials Science and Engineering State Key Laboratory of Silicon MaterialsZhejiang UniversityHangzhou310027China

Advanced electromagnetic(EM)wave absorbers with wide bandwidth is crucial to avoid EM interference and radiation,while achieving compensatio nal attenuation at different frequencies is challe ***,two-dimensional(2 D)sandwiched FeNi@SnO_(2)have been designed,for which SnO_(2)nanosheets provide numerous heterogeneous nucleation sites for the growth of dispersive FeNi nanoparticles with reduced *** SnO_(2)exhibits dipole polarization at 21.45 GHz with a width of~4.00 GHz,while the FeNi nanoparticles induce excha nge resonance at 18.13 GHz(~6.00 GHz width)and interfacial polarization at15.97 GHz(~6.00 GHz width).Such complementary attenuation mechanisms give rise to an impressive ultra-wide effective absorption bandwidth of 11.70 GHz with strong absorption of-49.1 dB at a small thickness of 1.75 *** only superior EM wave absorption is achieved in this work,it also provides a versatile strategy to integrate different loss mechanisms in the design of EM wave absorbers with extra-wide bandwidth.

关键词： Sandwiched FeNi@SnO_(2)nanosheets dielectric polarization Exchange resonance Complementary attenuation Electromagnetic wave absorption

Optimizing magnetic/dielectric matching in permalloy/carbonized cotton fiber composites by strain-tunable ferromagnetic resonance and defect-induced dielectric polarization

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Journal of Materials Science & Technology 2022年第29期124卷 174-181页

作者： Xiaochen Shen Chenglong Hu Wenling Ren Rongzhi Zhao Lianze Ji Xuefeng Zhang Xinglong Dong Key Laboratory of Materials Modification by Laser Ion and Electron BeamsSchool of Materials Science and EngineeringDalian University of TechnologyDalian 116023China Key Laboratory for Anisotropy and Texture of Materials(MOE) School of Materials Science and EngineeringNortheastern UniversityShenyang 110819China Institute of Advanced Magnetic Materials College of Materials and Environmental EngineeringHangzhou Dianzi UniversityHangzhou 310012China

Electromagnetic losses in composites could be synergistically controlled by permeability and permittivity,associated with multiple ferromagnetic resonances and dielectric ***,it is still challenging for simultaneous tunability for both the terms in a magnetic/dielectric composite ***,we demonstrate the tunable ferromagnetic resonances and the enhanced dielectric losses at gigahertz frequencies in permalloy/carbonized cotton fiber composites with different annealing *** is theoretically confirmed that the stress field acting on the magnetic permalloy layer increases with increasing temperature because of the shrinkage of the dielectric carbonized cotton fibers,resulting in multiple ferromagnetic resonances,in which there is a linear relationship(f=1.52×σ+9.38)between the resonance frequency(f)and the stress(σ).The present work provides a fundamental insight into understanding the micromagnetic dynamics of the magnetic/dielectric composite system.

关键词： Ferromagnetic resonance Stress tuning dielectric polarization

dielectric polarization of Ba2Ti9O20 Ceramics for Microwave Applications

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Dielectric Polarization of Ba2Ti9O20 Ceramics for Microwave ...

Size-Dependent Oxidation-Induced Phase Engineering for MOFs Derivatives Via Spatial Confinement Strategy Toward Enhanced Microwave Absorption

The 3～〔rd〕International Conference on High-Performance Ceramics(CICC-3)（1）

作者： Z.X. Xiong , F. Xiao , J.R. Huang and H. Qiu Department of Materials Science and Engineering and Department of Physics, Xiamen University,Xiamen 361005, China

dielectric constant of BaTiO ceramics are theoretically calculated based on the chemical structure of the oxides and the mixing rule of dielectric material in this paper. Meanwhile, the microwave properties (εr, Q and τf) of practical Ba2Ti9O20 ceramics are experimentally measured at microwave frequencies. Some of useful suggestions are therefore provided for material optimization of practical ceramics.

关键词： Microwave ceramics dielectric polarization Ba2Ti9O20 oxide

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Nano-Micro Letters 2022年第6期14卷 294-307页

作者： Hanxiao Xu Guozheng Zhang Yi Wang Mingqiang Ning Bo Ouyang Yang Zhao Ying Huang Panbo Liu School of Chemistry and Chemical Engineering μNorthwestern Polytechnical UniversityXi’an 710129People’s Republic of China Key Laboratory of Magnetic Materials and Devices Ningbo Institute of Materials Technology&EngineeringChinese Academy of SciencesNingbo 315201People’s Republic of China MIIT Key Laboratory of Semiconductor Microstructure and Quantum Sensing Nanjing University of Science and TechnologyNanjing 210094People’s Republic of China Department of Mechanical and Materials Engineering University of Western OntarioLondonON N6A 5B9Canada

Precisely reducing the size of metal-organic frameworks(MOFs)derivatives is an effective strategy to manipulate their phase engineering owing to size-dependent oxidation;however,the underlying relationship between the size of derivatives and phase engineering has not been clarified so ***,a spatial confined growth strategy is proposed to encapsulate small-size MOFs derivatives into hollow carbon *** realizes that the hollow cavity shows a significant spatial confinement effect on the size of confined MOFs crystals and subsequently affects the dielectric polarization due to the phase hybridization with tunable coherent interfaces and heterojunctions owing to size-dependent oxidation motion,yielding to satisfied microwave attenuation with an optimal reflection loss of-50.6 d B and effective bandwidth of 6.6 ***,the effect of phase hybridization on dielectric polarization is deeply visualized,and the simulated calculation and electron holograms demonstrate that dielectric polarization is shown to be dominant dissipation mechanism in determining microwave *** spatial confined growth strategy provides a versatile methodology for manipulating the size of MOFs derivatives and the understanding of size-dependent oxidation-induced phase hybridization offers a precise inspiration in optimizing dielectric polarization and microwave attenuation in theory.

关键词： Size-dependent oxidation Phase engineering Coherent interface dielectric polarization Electron holography

In Situ X-Ray Diffraction Study on Surface Melting of Bi Nanoparticles Embedded in a Si02 Matrix

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Chinese Physics Letters 2014年第1期31卷 136-139页

作者：陈晓明霍开拓刘鹏 College of Physics and Information Technology Shaanxi Normal University Xi ' an 710119

Bi nanoparticles embedded in a Si02 matrix were prepared via the high energy ball milling method. The melting behavior of Bi nanopartieles was studied by means of differential scanning calorimetry （DSC） arid high- temperature in situ X-ray diffraction （XRD）. DSC cannot distinguish the surface melting from ＇bulk＇ melting of the Bi nanoparticles. The XRD intensity of the Bi nanopartieles decreases progressively during the in situ heating process. The variation in the normalized integrated XRD intensity versus temperature is related to the average grain size of Bi nanoparticles. Considering the effects of temperature on Debye Waller factor and Lorentz-polarization factor, we discuss the XRD results in accordance with surface melting. Our results show that the in situ XRD technique is effective to explore the surface melting of nanoparticles.

关键词： NANOPARTICLES X-ray diffraction DIFFRACTION of electromagnetic waves polarization (Electricity) dielectric polarization

DIPOLE polarization RELAXATION AND MOLECULAR STRUCTURE OF MAIN-AND SIDE-CHAIN LIQUID-CRYSTALLINE POLYMERS

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Chinese Journal of Polymer Science 1996年第1期14卷 1-18页

作者： T.P.Stepanova L.L.Burshtein Institute of Macromolecular Compounds of Russian Academy of Sciences Bolshoy pr. 31 St. Petersburg 199004 RussiaInstitute of Macromolecular Compounds of Russian Academy of Sciences Bolshoy pr. 31 St. Petersburg 199004 Russia

Molecular mobility in thermotropic polyesters and side-chain polymers with different struc-ture of mesogens and spacers has been studied by dielectrical method in dilutesolutions. The results made it possible to establish the multiplicity of dielectric relaxationtransitions which reflects the small- and large-scale types of molecular motion. It was shownthat dielectric relaxation processes occurring in accordance with local mechanism (relaxationtimes 10^(-9)--10^(-7)s. and the activation energy 10--50kJ/mol) are due to the mobility of kineticchain elements of different length within a monomer units. It was found that the dielectricrelaxation process connected with a large-scale form of molecular motion (relaxation times10^(-5)--10^(-6)s. and the activation energy 100kJ/mol) did not depend on the molecular massbut was infiuenced by factors changing the conformational state of the macromolecule. It isestablished tha the cooperative reorientation mobility of associated mesogenic fragments isthe source of the large-scale process.

关键词： Liquid crystal polymers dielectric polarization Relaxation transitions Dilute solution Aggregation

Evidence of a third kind of Johnscher’s like universal dielectric response

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Journal of Advanced dielectrics 2018年第4期8卷 43-48页

作者： Maheswar Panda Department of Physics Dr.Harisingh Gour Vishwavidyalaya(A Central University)Sagar Madhya Pradesh 470003India

Polymer/metal composites(PMC)comprising of polyvinylidene fluoride/nanocrystalline nickel with varying volume fractions of nickel(fcon)prepared under cold press show an insulator to metal transition(IMT)at percolation threshold(f_(c)=f_(con)=0:27).The two kinds of generalized Johnscher’s universal dielectric response(UDR)laws on both sides of IMT hold good,while for the percolative sample,none of the two laws hold *** the concept of dipolar relaxation nor anomalous low frequency dispersion stands valid for f_(c)=0:27,while a completely different,neutral and competing electrical behavior is observed over the entire range of *** emerged third kind of Johnscher’s like UDR for fc is observed and the relaxation law has been formulated as the ratio of imaginary and real parts of dielectric constant remains constant over the entire range of frequency starting from dc to any higher *** value of the constant is attributed to depend on the PMC,the dielectric constant of the polymer,the differences of conductivity and fractions of the components of the PMC and also on their connectivity arising due to the difference of their process *** emerged unique dielectric relaxation consists of multiple relaxations arising due to the combination of other relaxations(arising due to the two different types of species)present in the sample,f_(con)=0:*** novel material may be suitable for certain specific applications in electrical and electronics engineering.

关键词： dielectric losses dielectric materials dielectric measurements dielectric polarization frequency response image analysis impedance measurement polymers relaxation processes spectroscopy

Surface potential uniformity and sensitivity of large-area PTFE electret discs of different thicknesses produced by a modified corona poling rotating system for dosimetry applications

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Journal of Advanced dielectrics 2019年第6期9卷 52-62页

作者： A.Komeijani H.Bagheri B.Shekarchi AJA Radiation Sciences Research Center(ARSRC)Science and Research Branch AJA University of Medical Sciences Tehran Iran

In this study,large-area(6-cm diameter)Teflon polytetrafluoroethylene(PTFE)discs of different thicknesses(0.2-,0.5-and 1-mm)were negatively and positively charged by using the“modified single point-to-plane corona poling rotating system”.The effects of some crucial parameters of the PTFE disc as well as the modified corona poling rotating system on the PTFE surface potential uniformity such as.(a)PTFE disc thickness,(b)PTFE disc polarity and(c)needle-to-PTFE disc distance were successfully ***,closer needle-to-PTFE disc distance,positive charging mode and thinner PTFE disc provided a better PTFE surface potential ***,the effects of PTFE charge polarity and needle distance on the electrostatic charge potential uniformity were much more remarkable in comparison with the effects of PTFE ***,the surface potential distribution profiles of charged PTFE discs were totally flat and independent of the PTFE thickness at 5-and 13-mm needle distances for the negative and positive charging modes,*** the optimized charging conditions,large-area PTFE electret disc(0.5-mm-thick)with positive uniform surface charge potential especially at the edges up to1.8 kV with stability up to 77 days studied was produced by applying a new multiple heat treatment protocol to the PTFE disc for radon *** also observed in this study,the sensitivity of PTFE electret dosimeters to a defined radon gas concentration increases as the PTFE thickness ***,0.5-mm-thick PTFE electret disc produced was selected to be used as a high quality electret dosimeter with acceptable and superior parameters for different applications in particular medium-term radiation dosimetry in both low and high dose rate ionizing radiation fields.

关键词： PTFE electrets dielectric polarization surface charge uniformity and stability electrostatic discharges and measurements dosimetry

Phenomenological Theory of Pyroelectricity

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材料科学与工程（中英文B版） 2020年第2期10卷 49-52页

作者： Manfred Fähnle Manfred Fhnle 71272 RenningenSchönblickstraße 95former member of Max Planck Institute for Intelligent SystemsStuttgart 70569Heisenbergstraße 3Germany

In pyroelectric materials there is a spontaneous dielectric *** raising the temperature,then a voltage appears in the *** the present manuscript a phenomenological theory of pyroelectricity is developed.

关键词： Pyroelectricity dielectric polarization phenomenological theory magnetism magnetostriction thermal expansion pyromagnetism

Large effective piezoelectric response from the spontaneously polarized surface layer in P(VDF-TrFE)arch films

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Journal of Advanced dielectrics 2022年第6期12卷 40-47页

作者： Xinping Hu Yuhong Zhu Baojin Chu CAS Key Laboratory of Materials for Energy Conversion and Department of Materials Science and Engineering University of Science and Technology of China No.96 Jinzhai Rd.HefeiAnhui 230026P.R.China

In this work,we show that a d_(33)~150 pC/N can be obtained in nonpoled poly(vinylidene fluoride trifluoroethylene)(P(VDF-TrFE))copolymer films with an arch *** copolymer films,which are often thought to be homogeneous,are in fact inhomogeneous in microstructure and physical properties after film *** a large proportion of the copolymer film is nonpolar,as expected in a nonpoled ferroelectric film,the surface regions of the film are spontaneously *** propose that inhomogeneous stress in the surface regions,which is either from the constraint of the substrate or skin layer effect formed during the film fabrication,generates a flexoelectric response and orients the spontaneous polarization of the ferroelectric *** a result of the polar surface regions,the nonpoled films exhibit a piezoelectric *** piezoelectric response is further amplified by the special arch structure of the films,leading to the observed large effective piezoelectric *** study not only discovers the polar surface effect in ferroelectric polymer films,but also proposes an approach to design polymer materials with a strong piezoelectric response.

关键词： Ferroelectric films dielectric polarization piezoelectricity surfaces